The design and construction of a new aircraft are very complex and extremely costly processes. Therefore an aircraft manufacturer who plans a new aircraft model, attempts to determine—before the actual design and development phase starts—in particular what technical operational and economic characteristics the envisaged new aircraft model should have in order to be successful commercially and therefore justify the high development costs.
Up until now it has been customary to do this by inviting representatives of airlines, and therefore representatives of potential customers, to what are referred to as customer focus group or airline advisory board events. At these events, the representatives of the airlines are asked to express requests regarding the configuration parameters of a new aircraft model. The configuration parameters enquired about include, for example, the desired payload (this relates essentially to the size of the fuselage with respect to the maximum number of passengers plus freight to be carried, for example), the range requirement, take off and landing requirements, the desired cruising altitude and, if appropriate, further configuration parameters such as, for example, the desired cruising speed, maximum values for the wing span, fuselage length and/or surface pressure per wheel of the landing gear.
The estimates regarding the configuration parameters which are issued by the representatives of the airlines are subsequently compiled and evaluated statistically. The aircraft manufacturer will then define configuration parameters determined on the basis of the statistical evaluation and according to further questioning of experts, as a configuration point for the new aircraft model.
On the basis of the configuration point determined in this way, a synthesis method is then applied which permits an aircraft design which satisfies the configuration point to be iteratively optimized in terms of the costs. The corresponding synthesis method according to the prior art is, inter alia, described in “Synthesis of Subsonic Airplane design: An introduction to the preliminary design of subsonic general aviation and transport aircraft, with emphasis on layout, aerodynamic design, propulsion and performance” by Egbert Torenbeek, published 1982 by Delft University Press, 9th Reprint 1999, and in “Advanced Aircraft Design: Conceptual Design, Technology and Optimization of Subsonic Civil Airplanes” by Egbert Torenbeek, published 2013 by John Wiley & Sons.
In the synthesis method, firstly dimensioning of the propulsion system, wings and empennage, mass estimation resulting therefrom together with the parameters of the configuration point and preliminary estimation of flight performance are optimized iteratively in such a way that the maximum takeoff weight converges and the range requirements and take off and landing requirements are satisfied according to the configuration point. Subsequently, a cost estimation is made for a correspondingly optimized design, wherein, in particular, the later operating costs are estimated. It is then checked whether the design is that which is optimum in terms of costs. If this is not the case, the iteration described above is frequently repeated with other output variables (for example the dimensioning of the propulsion system) until cost optimum is achieved.
The method described gives rise to an aircraft design which is optimized in terms of the predefined configuration point. However, in the methods known from the prior art it is not ensured that the configuration point to which the aircraft design is optimized is also selected in an optimum way. For example, in the prior art the ultimate configuration point is defined on the basis of customer consultations and subjective expert opinions, which undeniably entails the risk of selecting an “incorrect configuration point”. As a result, an aircraft can be dimensioned “beyond market requirements” and will then only find few customers, if any at all. The consequences can be “fatal” owing to the high development costs for the aircraft manufacturer.